In neuroscience, quantum brain dynamics (QBD) is a hypothesis to explain the function of the brain within the framework of quantum field theory. Although there are many blank areas in understanding the brain dynamics and especially how it gives rise to conscious experience it should be noted that quantum mechanics is only conisdered by some to be capable of explaining the enigma of consciousness. There is currently no experimental verification of this hypothesis. QBD is thus classified as protoscience.

Mari Jibu and Kunio Yasue (1995) were the first researchers that tried to popularize the quantum field theory of Nambu-Goldstone bosons as the one and only reliable quantum theory of fundamental macroscopic dynamics realized in the brain with which a deeper understanding of consciousness can be obtained. This hypothesis was originated by Ricciardi and Umezawa (1967) in a general framework of the spontaneous symmetry breaking formalism, and since then developed into a quantum field theoretical framework of brain functioning called quantum brain dynamics (Jibu and Yasue 1995) and that of general biological cell functioning called quantum biodynamics (Del Giudice et. al., 1986; 1988). There, Umezawa proposed a general theory of quanta of long-range coherent waves within and between brain cells, and showed a possible mechanism of memory storage and retrieval in terms of Nambu-Goldstone bosons characteristic to the spontaneous symmetry breaking formalism.